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Exhausting of flux in reflow ovens

lima

#11464

Exhausting of flux in reflow ovens | 13 May, 1999

Does anyone know of any industry guidelines for the exhausting of volatiles in reflow ovens? I've seen some numbers like 1,000ppm for the oven atmosphere, but is this typical?

My concern is the volatiles in my WS629 solder paste may be attacking the ink marking on the metal surfaces of some components. The markings pass the standard permanence tests, but we've seen that the combination of paste and de-ionized water can strip the ink from the surface. It's not clear to me whether the main damaging effect occurs during reflow or during the subsequent 140C DI water wash. I'm just looking for information that might rule out the Conceptronic oven as the culprit. Perhaps not enough of the flux is being burned off during reflow, and enough is present during the wash stage?

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Mike Dreyer

#11465

Re: Exhausting of flux in reflow ovens | 14 May, 1999

| Does anyone know of any industry guidelines for the exhausting of volatiles in reflow ovens? I've seen some numbers like 1,000ppm for the oven atmosphere, but is this typical? | | My concern is the volatiles in my WS629 solder paste may be attacking the ink marking on the metal surfaces of some components. The markings pass the standard permanence tests, but we've seen that the combination of paste and de-ionized water can strip the ink from the surface. It's not clear to me whether the main damaging effect occurs during reflow or during the subsequent 140C DI water wash. I'm just looking for information that might rule out the Conceptronic oven as the culprit. Perhaps not enough of the flux is being burned off during reflow, and enough is present during the wash stage? | Sounds like you need a good set of experiments to determine the main culprit. You might want to check on your components intermittently as you pass them through the process or you may want to run a simple set of tests, running various experiments, keeping all parameters constant ( except one that you want to test ). For example, if I were suspect of the DI water having an effect on the components, I would take some components(unbaked) and run them through the cleaner ( eliminates the affect of the oven on the components ). Then I would run them through some other similar tests using the parameters you were concerned about( i.e. run components through oven with no paste, etc ). It may very well end up that a series of events cause the markings to "lighten" or disappear or it may be one cause. It may be just the heat affecting the markings as well, but you'll never know unless you perform some simple tests. Good Luck. Mike

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lima

#11466

Re: Exhausting of flux in reflow ovens | 14 May, 1999

| | Does anyone know of any industry guidelines for the exhausting of volatiles in reflow ovens? I've seen some numbers like 1,000ppm for the oven atmosphere, but is this typical? | | | | My concern is the volatiles in my WS629 solder paste may be attacking the ink marking on the metal surfaces of some components. The markings pass the standard permanence tests, but we've seen that the combination of paste and de-ionized water can strip the ink from the surface. It's not clear to me whether the main damaging effect occurs during reflow or during the subsequent 140C DI water wash. I'm just looking for information that might rule out the Conceptronic oven as the culprit. Perhaps not enough of the flux is being burned off during reflow, and enough is present during the wash stage? | | | Sounds like you need a good set of experiments to determine the main culprit. You might want to check on your components intermittently as you pass them through the process or you may want to run a simple set of tests, running various experiments, keeping all parameters constant ( except one that you want to test ). For example, if I were suspect of the DI water having an effect on the components, I would take some components(unbaked) and run them through the cleaner ( eliminates the affect of the oven on the components ). Then I would run them through some other similar tests using the parameters you were concerned about( i.e. run components through oven with no paste, etc ). It may very well end up that a series of events cause the markings to "lighten" or disappear or it may be one cause. It may be just the heat affecting the markings as well, but you'll never know unless you perform some simple tests. Good Luck. Mike | Mike, Thanks for the response. Unfortunately we have the usual conundrum of a low-frequency but ongoing problem (~1-2%) combined with a lack of sample parts to play around with. I do know that putting gobs of flux/paste on the edges of a part, running it through the oven, and swabbing the marked surface with water does strip off some of the ink. Water by itself has negligible effect. Heat by itself has negligible effect. Thus I suspect that the volatiles or residue from the paste must play a role...I just don't know whether I need to be concerned with the vapors in the oven or whether the detrimental exposure just occurs in the wash process.

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